Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$190.48	5.818%	$201.5621	$201.56	$201.55	$201.60
Purchase #2	$177.51	6.624%	$189.2683	$189.27	$189.25	$189.30
Purchase #3	$130.48	13.301%	$147.8351	$147.84	$147.85	$147.80
Purchase #4	$64.57	4.589%	$67.5331	$67.53	$67.55	$67.50
Purchase #5	$132.56	5.566%	$139.9383	$139.94	$139.95	$139.90
Purchase #6	$127.72	6.737%	$136.3245	$136.32	$136.30	$136.30
Purchase #7	$191.68	9.316%	$209.5369	$209.54	$209.55	$209.50
7 purchase totals =	$1,015.00		$1,091.9983	$1,092.00	$1,092.00	$1,091.90